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Abstract The present paper describes an experimental study on mechanical properties of additively manufactured anti-tetrachiral auxetic structures under shear and flexural loading. Specimens of ABS material are fabricated using material [...]

Gas flotation for oily wastewater treatment is based on the attachment of gas bubbles to oil droplets to produce lighter aggregates that rise to the wastewater surface. It is a feasible, promising, and effective method for oily wastewater treatment due to its high separation efficiency with no secondary contamination, cost-effectiveness, and simple operation. This review focuses on separating oil from emulsions by gas flotation using microbubbles (MBs) and nanobubbles (NBs), which offer the advantages of small bubble size, large specific surface area, and slow rising velocity. The properties of different types of gas bubbles and their generation methods were discussed. Different gas flotation system designs and operational parameters were summarized for dissolved gas flotation, induced gas flotation, and electrolytic flotation (EF). The review illustrated that oil removal efficiency in MB- and NB-based gas flotation was affected by various factors including initial oil concentration, pH, temperature, flotation time, and oil droplet size. Key words: gas flotation, microbubble, nanobubble, oil-in-water emulsion, oily wastewater treatment La flottation gazeuse pour le traitement des eaux usées contaminées par les hydrocarbures est basée sur la fixation des bulles de gaz aux gouttelettes d'hydrocarbures pour produire des agrégats plus légers qui remontent àla surface des eaux usées. Il s'agit d'une méthode réalisable, prometteuse et efficace pour le traitement des eaux usées contaminées par les hydrocarbures en raison de sa grande efficacité de séparation sans contamination secondaire, de sa rentabilité et de sa simplicité d'utilisation. Cette synthèse se concentre sur la séparation des hydrocarbures des émulsions par flottation gazeuse en utilisant des microbulles et des nanobulles qui offrent les avantages d'une petite taille de bulle, d'une grande surface spécifique et d'une vitesse d'ascension lente. Les propriétés des différents types de bulles de gaz et leurs méthodes de génération ont été discutées. Les différentes conceptions de systèmes de flottation gazeuse et les paramètres opérationnels ont été résumés pour la flottation par gaz dissous, la flottation par gaz induit et la flottation électrolytique. La synthèse a montré que l'efficacité de l'élimination des hydrocarbures par la flottation gazeuse àbase de microbulles et de nanobulles était affectée par divers facteurs, notamment la concentration initiale d'hydrocarbures, le pH, la température, le temps de flottation et la taille des gouttelettes d'hydrocarbures. [Traduit par la Rédaction] Mots-clés : flottation gazeuse, microbulles, nanobulles, émulsion d'huile dans l'eau, traitement des eaux usées contaminées aux hydrocarbures, 1 Introduction Oily wastewater is generated from oil spill incidents and many other sources, such as food processing, oil refining, textile and leather industries, metal rolling and finishing, paper deinking, [...]

In the present work, an experimental investigation is performed to study the influence of process parameters on mechanical properties of tetra-anti-chiral auxetic structures manufactured by material extrusion (ME) technique of additive manufacturing (AM). Process parameters namely layer height, print speed, and print temperature are considered, while responses are compressive strength ([sigma]), modulus (E), and specific energy absorption (SEA). Specimens of acrylonitrile-butadiene-styrene (ABS) polymer are fabricated and then tested under compressive loading. From the experimental results, it is observed that all process parameters significantly influence the mechanical properties of the structure. Scanning electron microscope (SEM) is used to study microstructural defects of the tested specimen. To maximize the responses, optimization of process parameter is performed using desirability function approach. Regressive models are developed to predict the mechanical properties. KEYWORDS additive manufacturing, chiral, compression, mechanical properties, modulus, strength, 1 | INTRODUCTION Cellular materials are used in lightweight sandwich panels, which have wide industrial applications due to high stiflhess-to-weight ratio and impact energy absorption. [1] Metamaterials, also known as [...]

Author(s): Joong Hwan Bahng [sup.1] , Bongjun Yeom [sup.2] , Yichun Wang [sup.1] , Siu On Tung [sup.3] , J. Damon Hoff [sup.4] , Nicholas Kotov [sup.1] [sup.2] [sup.3] [sup.5] [...], Micrometre-sized particles covered with stiff, nanoscale spikes are shown to exhibit long-term colloidal stability in both hydrophilic and hydrophobic media, without the need for chemical coating, owing to the effect of the spikes on the contact area and, consequently, the force between the particles. A new way of forming colloidal suspensions The conventional way of persuading hydrophobic particles to form colloidal suspensions in water -- and hydrophilic particles to disperse in oil -- is to camouflage the particles chemically with surfactants, organic tethers, adsorbed polymers or other agents that impart affinity for the solvent. Joong Hwan Bahng et al. now show that surface corrugation provides a very effective alternative strategy for dispersing particles in a wide range of solvents. The team produce micrometre-sized 'hedgehog' particles that are coated with stiff nanospikes and exhibit long-term colloidal stability in both hydrophilic and hydrophobic media. This unusual dispersion behaviour challenges current theories and deepens our understanding of colloidal interparticle interactions. The technique may have technological uses, as it provides particles that function in both organic and aqueous media. Hydrophobic particles in water and hydrophilic particles in oil aggregate, but can form colloidal dispersions if their surfaces are chemically camouflaged with surfactants, organic tethers, adsorbed polymers or other particles that impart affinity for the solvent and increase interparticle repulsion.sup.1,2. A different strategy for modulating the interaction between a solid and a liquid uses surface corrugation, which gives rise to unique wetting behaviour.sup.3,4,5. Here we show that this topographical effect can also be used to disperse particles in a wide range of solvents without recourse to chemicals to camouflage the particles' surfaces: we produce micrometre-sized particles that are coated with stiff, nanoscale spikes and exhibit long-term colloidal stability in both hydrophilic and hydrophobic media. We find that these 'hedgehog' particles do not interpenetrate each other with their spikes, which markedly decreases the contact area between the particles and, therefore, the attractive forces between them. The trapping of air in aqueous dispersions, solvent autoionization at highly developed interfaces, and long-range electrostatic repulsion in organic media also contribute to the colloidal stability of our particles. The unusual dispersion behaviour of our hedgehog particles, overturning the notion that like dissolves like, might help to mitigate adverse environmental effects of the use of surfactants and volatile organic solvents, and deepens our understanding of interparticle interactions and nanoscale colloidal chemistry.

Hydrophobic particles in water and hydrophilic particles in oil aggregate, but can form colloidal dispersions if their surfaces are chemically camouflaged with surfactants, organic tethers, adsorbed polymers or other particles [...]

Author(s): David Chandler (corresponding author) [1] Most general chemistry students are taught how detergent removes grease. An essential aspect of this process depends on the amphiphilic nature of the detergent [...]

Author(s): Philip Ball [1] Water is notorious for behaving strangely, but it is possible that we don't yet know the half of it. Amid the crush of biological macromolecules and [...]

Author(s): Seema Singh [1]; Jack Houston [1]; Frank van Swol [1, 2]; C. Jeffrey Brinker (corresponding author) [1, 2] Long-range hydrophobic interactions operating underwater are important in the mediation of [...]